New server unable to join exisiting cluster

Hi all,
I have two servers Dev01, and Dev02 (both with subnet mask of 225.225.225.0)
setup in a cluster.
This works just fine.
I tried to add a new server (Dev03) into the cluster but the log file
states that " waited for 30s and no initial state was set by the discovery"
and then makes this server the new master.
This machine is in a subnet with a mask of 225.225.224.0.
This is the only difference between the three mmachines.
Can this be a reason why this server cannot connect to Dev01 and Dev02 ??
If yes, is there a way wherein i can make this happen ?
For all my servers the yml file contains the following props:

  1. cluster.name: DevCluster
  2. node.name: (Individual names of the machines for easy understanding)
  3. discovery.zen.ping.timeout: 60s

I have tried setting the discovery.zen.ping.unicast.hosts: ["IP addresses
of Dev01 and Dev02"] on Dev03 but this doesnt help either.
Could anyone point me in the right direction ?
Thanking in advance.

regards,
-Parag